Understanding Attributes in ABAP Object-Oriented Programming
In Object-Oriented Programming (OOP), an attribute refers
to a property or characteristic of an object or class. In ABAP, attributes hold
data values and describe the state of an object or class.
For example, if you have a class to represent a car, the
attributes could be things like color, model, speed, etc.
---
Types of Attributes in ABAP OOP
There are two main types of attributes in ABAP:
1. Instance Attributes
2. Static Attributes
1.
Instance Attributes
Instance attributes are specific to each object of a
class. Every object (or instance) has its own set of instance attributes.
Changes made to instance attributes of one object do not affect other objects.
- Example:
If you create two different car objects, one car can have a color attribute set to red, while another car can have the color set to blue.
- Usage in ABAP:
abap
CLASS lcl_car DEFINITION.
PUBLIC SECTION.
DATA: color TYPE string. " Instance Attribute
ENDCLASS.
CLASS lcl_car IMPLEMENTATION.
ENDCLASS.
DATA: car1 TYPE REF TO lcl_car,
car2 TYPE REF TO lcl_car.
CREATE OBJECT car1.
car1->color = 'Red'.
CREATE OBJECT car2.
car2->color = 'Blue'.
WRITE: / 'Car 1 color:', car1->color.
WRITE: / 'Car 2 color:', car2->color.
Output:
Car 1 color: Red
Car 2 color: Blue
Each object (car1, car2) has its own color value.
2.
Static Attributes
Static attributes belong to the class itself, not to any particular object. All objects of the class share the same static attribute, meaning if one object changes the static attribute, it affects all other objects of the class.
- Example:
If you create two different car objects, but there is a static attribute like total_number_of_cars, all objects will share the same value.
- Usage in ABAP:
abap
CLASS lcl_car DEFINITION.
PUBLIC SECTION.
CLASS-DATA: total_number_of_cars TYPE
i. " Static Attribute
ENDCLASS.
CLASS lcl_car IMPLEMENTATION.
ENDCLASS.
DATA: car1 TYPE REF TO lcl_car,
car2 TYPE REF TO lcl_car.
CREATE OBJECT car1.
lcl_car=>total_number_of_cars = 1. " Static attribute
CREATE OBJECT car2.
lcl_car=>total_number_of_cars =
lcl_car=>total_number_of_cars + 1.
WRITE: / 'Total number of cars:',
lcl_car=>total_number_of_cars.
Output:
Total number of
cars: 2
Both objects share the same total_number_of_cars attribute, and the change affects all objects.
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Key Differences
Between Instance and Static Attributes
|
Aspect |
Instance Attribute |
Static Attribute |
|
Ownership |
Belongs to each
individual object |
Belongs to the
class itself |
|
Scope |
Specific to an
object |
Shared by all
instances of the class |
|
Lifetime |
Exists as long as
the object exists |
Exists for the
lifetime of the class |
|
Change Effect |
Changes affect only
that object |
Changes affect all
objects of the class |
---
Using Attributes in an ABAP OOP Program
Here is an example where both instance and static attributes are used:
abap
CLASS lcl_car
DEFINITION.
PUBLIC SECTION.
DATA: color TYPE string. " Instance Attribute
CLASS-DATA: total_number_of_cars TYPE
i. " Static Attribute
METHODS: display_details.
ENDCLASS.
CLASS lcl_car
IMPLEMENTATION.
METHOD display_details.
WRITE: / 'Car color:', color, 'Total
cars:', total_number_of_cars.
ENDMETHOD.
ENDCLASS.
DATA: car1 TYPE REF
TO lcl_car,
car2 TYPE REF TO lcl_car.
CREATE OBJECT car1.
car1->color =
'Red'.
lcl_car=>total_number_of_cars
= lcl_car=>total_number_of_cars + 1.
CREATE OBJECT car2.
car2->color =
'Blue'.
lcl_car=>total_number_of_cars
= lcl_car=>total_number_of_cars + 1.
car1->display_details().
car2->display_details().
Output:
Car color: Red
Total cars: 2
Car color: Blue
Total cars: 2
In this example:
- Each car object has its own color (instance attribute).
- Both objects share the same static attribute total_number_of_cars.
---
Conclusion
Attributes play a crucial role in describing the
properties of an object in ABAP OOP. Instance attributes are unique to each
object, while static attributes are shared among all instances of the class. By
understanding these concepts, you can design more efficient and organized
object-oriented programs.